There are many applications involving the emission or reception of optical radiation where being able to limit the solid angle of the path over which an optical beam travels can have significant benefits.
From another aspect, reducing multipath reflections from optical beams significantly increases the usable bandwidth of optical communication links.
One example, which is not meant to be limiting, is directed to a system for a room or other enclosure containing, at arbitrary locations, a large number of devices and one central diffuse infrared (IR) radiation source, the object of which is to locate one or more particular devices and lock onto them with stationary directed beams.
In a large room, radiation from a diffuse IR source travels in all directions. Light beams scattered from various surfaces in the room arrive with varying time delays at a given receiver, causing significant limitations on the bandwidth of transmitted data. This multipath problem limits the communication bandwidth to on the order of (3.0.times.10.sup.8 m/sec)/d, where d is a characteristic length for the room. In practice, this can limit the usable bandwidth to under 10 Mbit/sec.